The present invention relates generally to the field of electrically insulative devices, and more particularly, but not by way of limitation, to an improved insulator for the disposal of high voltage power supply wires used in comnmercial electrical signs.
Electrical signs used commercially to advertise a business or event typically require high voltage power supply wires to transfer electrical power from a power distribution source to the point of power termination within the sign. Neon signs in particular commonly employ step-up transformers that generate secondary side voltages in the range of five to fifteen thousand volts. With such relatively high secondary side voltages, wires have commonly been found to prematurely fail over time, causing a short circuiting of the supply power to the sign enclosure. These electrical failures can create a dangerous safety hazard to personnel working in and around the sign and can initiate an electrical fire resulting in the catastrophic loss of property and lives.
Such failures usually stem from a breakdown of insulation between the wire's conductors and a grounded conductive portion of the sign. Although the power supply wires typically employ the use of an insulative sheath, the sheath alone commonly does not provide reliable protection when subjected to the harsh and continuous duty operation conditions characteristic of a high voltage sign.
In a commercial sign the power supply wire is generally passed through an opening in a substantially planar boundary, such as through a wall of an enclosure (sometimes referred to as a can), which is typically made of a conductive material such as aluminum or sheet metal. The boundary may also comprise a facia of a sign or a structural member such as plywood, sheetrock, concrete and the like.
Insulators of various types have been employed to electrically insulate the wire from the boundary to prevent short circuiting and failure of the wire. Such insulators have been fabricated using well known electrically insulative materials such as rubber, plastic, and the like. No insulator has been found to date, however, that will consistently and reliably prevent premature short circuit failures.
One solution commonly employed by those skilled in the art to minimize electrical shorting is to fabricate an insulator for the wires for a glass slip stick comprising a hollow, cylindrical member. To do so, an operator passes the wire through the slip stick and secures the slip stick in the boundary opening using a suitable caulking material, such as silicon.
Although the use of slip sticks has been found to provide improved electrical insulation for wires in a commercial sign application, limitations are associated with this approach. First, the process of installing the slip sticks is labor and material intensive, especially for large signs which may require the fabrication of tens, or even hundreds of such hand-crafted insulators.
Second, there is a risk of injury to the operator through the handling of the slip sticks, should one be inadvertently broken during installation. Third, the resulting insulator can distract from the cosmetic appearance of the sign, especially when the insulators are visible when a passerby views the sign. Finally, the process does not completely prevent failure, as over time the caulking materials can adsorb moisture or dry out and crack, leading to an eventual failure of the sign.
Accordingly, there is a need for an improved approach to insulating high voltage wires in a commercial sign application that is easily installed, cosmetically appealing, and reliable in operation.